Iranian authorities have again extended the temporary release of jailed British-Iranian aid worker Nazanin Zaghari-Ratcliffe, her family and lawyer say.

In mid-March, Zaghari-Ratcliffe was temporarily released from Tehran's Evin prison, where she was serving of a five-year sentence for 'plotting to topple the Iranian government,' a charge she has denied.

The furlough has been extended until May 27, her lawyer told the IRNA news agency on May 20.

Mahmud Behzadirad added that Zaghari-Ratcliffe had been told by judiciary officials that they would decide whether the rest of her sentence will be commuted.

'Nazanin spoke to the Prosecutors Office today. Her furlough from prison has again been extended -- until a decision has been made on her clemency. She was told no decision has been made on clemency,' the Free Nazanin campaign tweeted.

Amnesty International U.K.'s director, Kate Allen, said that 'another period of this 'conditional liberty' is far better than outright jail, but we're worried that the Iranian authorities are still playing games with Nazanin and her family.'

'Confined to her parents' house in Tehran, Nazanin is still a prisoner of conscience,' Allen said in a statement.

A project manager with the Thomson Reuters Foundation, Zaghari-Ratcliffe was arrested in April 2016 at a Tehran airport as she headed back to Britain with her daughter following a family visit.

She was sentenced to prison in September 2016 following what Amnesty International called a 'deeply unfair trial.'

Britain has demanded her release and that of other dual nationals imprisoned in Iran. Tehran does not recognize dual citizenship.

Iran has temporarily released tens of thousands of inmates, including political prisoners, in recent months in response to the coronavirus epidemic.